U.S. patent number 6,067,559 [Application Number 09/066,742] was granted by the patent office on 2000-05-23 for server architecture for segregation of dynamic content generation applications into separate process spaces.
This patent grant is currently assigned to Microsoft Corporation. Invention is credited to James E. Allard, Mark T. Anders, Lei Jin, David L. Kaplan, Murali R. Krishnan, Seth B. Pollack, Andrew Sigal.
United States Patent |
6,067,559 |
Allard , et al. |
May 23, 2000 |
Server architecture for segregation of dynamic content generation
applications into separate process spaces
Abstract
A server architecture has a server program to receive client
requests and multiple applications to process the requests. Each
application comprises a collection of agents that can be invoked to
process the requests and an application manager that manages the
collection of agents. The agents within the associated collection
are independent from, but dynamically accessible by, the
application manager. Depending on the request, the application
manager selects one or more agents to generate content to be
returned to the client. An application manager director manages the
application managers and facilitates delivery of the client
requests from the server program to the suitable application. The
application managers are independent from, but dynamically
accessible by, the application manager director. For a given
request, the director selects the appropriate application manager
to handle the request. The application manager, in turn, selects
the appropriate agent to process the request. The director can be
implemented as part of the server program. The applications,
including the agents and associated application managers, can be
run either in-process or out-of-process with the server
program.
Inventors: |
Allard; James E. (Seattle,
WA), Anders; Mark T. (Bellevue, WA), Jin; Lei
(Newcastle, WA), Kaplan; David L. (Mercer Island, WA),
Krishnan; Murali R. (Redmond, WA), Pollack; Seth B.
(Seattle, WA), Sigal; Andrew (Seattle, WA) |
Assignee: |
Microsoft Corporation (Redmond,
WA)
|
Family
ID: |
22071400 |
Appl.
No.: |
09/066,742 |
Filed: |
April 23, 1998 |
Current U.S.
Class: |
709/202; 709/219;
709/223; 715/205; 718/107 |
Current CPC
Class: |
G06F
9/5055 (20130101) |
Current International
Class: |
G06F
9/46 (20060101); G06F 9/50 (20060101); G06F
013/00 () |
Field of
Search: |
;709/100,101,102,107,202,203,217,219,223,225,226,300,302,303,304
;707/10,100,103,104,501 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Vu; Viet D.
Attorney, Agent or Firm: Lee & Hayes, PLLC
Claims
We claim:
1. A server system for handling client requests from one or more
clients, comprising:
one or more agent collections, each agent collection having one or
more agents, the agent collections being individually programmed to
handle different respective types of client requests;
one or more application managers, each application manager being
configured to manage a corresponding agent collection and to select
a particular agent from the corresponding agent collection to
process the client request; and
an application manager director to manage the one or more
application managers, the application manager director being
configured to select a particular application manager and to pass
the client request to the particular application manager for
processing by the particular agent selected by the particular
application manager.
2. A server system as recited in claim 1, wherein the application
manager director maintains a table that lists the application
managers that are running.
3. A server system as recited in claim 1, wherein said each
application manager maintains a table that lists the agents in the
corresponding agent collection that are running.
4. A server system as recited in claim 1, further comprising at
least two application managers, the application managers being run
in-process with one another.
5. A server system as recited in claim 1, further comprising at
least two application managers, the application managers being run
in separate processes from one another.
6. A server software architecture embodied on a computer-readable
medium for implementation on a computer server system, the server
software architecture comprising:
a server program to receive a client request from a client and
return a response to the client;
an application manager director to handle the client request in an
event that a response to the client request will involve at least
some content generation;
at least one application manager independent from, but dynamically
accessible by, the application manager director;
at least one agent independent from, but dynamically accessible by,
the application manager, the agent comprising a specialized
functionality to process particular types of client requests to
generate the response; and
upon receiving the client request, the application manager director
calls the application manager and passes the client request to the
application manager, the application manager calls the agent and
passes the client request to the agent, and the agent processes the
client request to generate the response.
7. A server software architecture as recited in claim 6, wherein
the application manager director creates a request object to hold
data from the client request.
8. A server software architecture as recited in claim 7, wherein
the application manager creates a shadow object to hold data from
the client request.
9. A server software architecture as recited in claim 7, wherein
the application manager director, the application manager, and the
agent all run in-process with the server program.
10. A server software architecture as recited in claim 7, wherein
the application manager and the agent run in a separate process
from the server program.
11. A server software architecture as recited in claim 7, further
comprising first and second application managers, the first
application manager being run in-process with the server program
and the second application manager being run in a separate process
from the server program.
12. A server software architecture as recited in claim 7, wherein
the application manager director maintains a table that lists the
application managers that are running.
13. A server software architecture as recited in claim 7, wherein
said each application manager maintains a table that lists the
agents that are running.
14. A dynamic content generation system embodied as computer
program modules on a computer-readable medium, the dynamic content
generation system being implemented in a server connected to serve
one or more clients, the dynamic content generation system
comprising:
code means for receiving a client request from a client;
code means for selecting an application manager based on an
application manager's functionality from a set of multiple
application managers having different defined functionalities, the
application managers being capable of running in process or out of
process;
code means for passing the client request to the selected
application manager;
code means for selecting an agent to process the client
request;
code means for passing the client request to the selected
agent;
code means for processing the client request at the selected agent
to dynamically create content that forms a response to the client
request; and
code means for transferring the response back to the client.
15. A server operating system comprising the dynamic content
generation system as recited in claim 14.
16. A server computer system comprising:
a processing unit;
a memory subsystem;
a server program stored in the memory subsystem and executed on the
processing unit to receive client requests; and
multiple applications stored in the memory subsystem and executed
on the processing unit either in-process or out-of-process with the
server program to dynamically generate responses to the client
requests, each said application comprising one or more agents to
process the client requests and an application manager to manage
the one or more agents, individual applications having different
programmed functionalities; and
an application manager director to facilitate delivery of the
client requests received by the server program to the applications
that are appropriate for processing the client requests, whereupon
receiving a specific client request, the application manager
director selects a particular application manager based upon an
application's functionality and forwards the specific client
request to the particular application manager, and the particular
application manager selects a particular agent and forwards the
specific client request to the particular agent for processing.
17. A server computer system as recited in claim 16, wherein the
application manager director maintains a table that lists the
application managers that are running and that indicates whether
the application managers are in-process or out-of-process.
18. A server computer system as recited in claim 16, wherein the
application manager maintains a table that lists the agents that
are running.
19. A server computer system as recited in claim 16, wherein:
the application manager director creates request objects to hold
data contained in the client request; and
the application managers create shadow objects for corresponding
request objects, the shadow objects holding at least a subset of
the data contained in the request objects.
20. A server operating system for execution on a server that is
configured to serve one or more clients, the server operating
system being implemented with a dynamic content generation system
for handling an HTTP request that involves dynamic generation of
content based on data included in the HTTP request, the dynamic
content generation system having a managerial hierarchy comprising
an application manager director, one or more application managers
that are dynamically accessible by the application manager director
to handle the client request, and one or more agents grouped in
accordance with predefined agent functionalities and in association
with the application managers and dynamically accessible by the
associated application managers to dynamically generate the content
in response to the HTTP request.
21. A computer-executable application manager object embodied on a
computer-readable medium for execution on a server computer, the
server computer running a server software program to receive and
process client requests from one or more clients and to return
responses to the client requests, the application manager object
comprising:
a flag field to hold data indicating whether the application
manager is in-process with the server software program or
out-of-process with the server software program;
a list of the client requests that are currently being
processed;
a table identifying one or more agent programs that are currently
running to process the client requests on the list; and
code means for selecting the agent programs for processing the
client requests.
22. An application manager object as recited in claim 21, wherein
the code means includes code means for starting an agent
program.
23. A method for handling client requests, comprising the following
steps:
receiving a client request from a client;
selecting an application manager suitable for handling the client
request;
passing the client request to the selected application manager;
selecting an agent to process the client request, the agent having
a programmed functionality that is associated with the type of
client request that is received;
passing the client request to the selected agent;
processing the client request at the selected agent to dynamically
create content that forms a response to the client request; and
transferring the response back to the client.
24. In a server system having a hierarchic managerial architecture
comprising an application manager director, one or more application
managers that are dynamically accessible by the application manager
director, and one or more agents grouped in association with the
application managers and dynamically accessible by the associated
application managers, a method for handling a client request
comprising the following steps:
creating a request object to hold data from the client request;
identifying an application manager from a set of multiple
application managers;
calling the identified application manager;
creating a shadow object in correspondence with the request object,
the shadow object holding at least a subset of the data contained
in the request object;
identifying an agent from a set of multiple agents; and
invoking the identified agent;
processing, within the identified agent, the data contained in the
shadow object to create a response;
returning the response; and
destroying the shadow object.
25. A method as recited in claim 24, wherein the calling step
comprises the step of calling an out-of-process application
manager.
26. A method as recited in claim 24, further comprising the step of
destroying the request object after said step of destroying the
shadow object.
27. A method as recited in claim 24, further comprising the step of
tracking the application managers that are running.
28. A method as recited in claim 24, farther comprising the step of
tracking the agents that are running.
29. A method as recited in claim 24, further comprising the step of
managing the agents and the application managers that are
running.
30. A method as recited in claim 24, farther comprising the step of
stopping, passing, and unloading the agents and the application
managers that are running.
Description
TECHNICAL FIELD
This invention relates to servers for computer network systems.
More particularly, this invention relates to a server architecture
that implements a dynamic content method for generating client
responses.
BACKGROUND OF THE INVENTION
A computer network system has one or more host network servers
connected to serve data to one or more client computers over a
network. FIG. 1 shows a simple computer network system 20 with a
single host network server 22 connected to serve data to a client
24 via a network 26. The client 24 sends a request for data and/or
services to the server 22 over the network 26. The server 22
processes the request and returns a response over the network 26.
If the request is for data, the server 22 accesses a database 28 to
retrieve the requested data 30 and returns the data 30 as part of
the response.
The client-server system 20 is representative of many different
environments. One particular environment of interest is the
Internet. The server 22 runs a Web server software program that
accepts requests from client-based programs (e.g., browsers) and
returns data 30 in the form of Web pages or documents to the client
24. The Web pages are commonly written in HTML (hypertext markup
language) and XML (extensible markup language). Web pages are
transmitted using conventional network protocols, such as TCP/IP
(Transmission Control Protocol/Internet Protocol), HTTP (Hypertext
Transfer Protocol) and DCOM (Distributed Component Object Model).
The client 24 executes a browser or other application to render the
Web page into human-perceptible forms. A Web document might include
text, images, sound, video, active code, and so forth.
Documents served from a server to client are typically generated
using either or both of two methods: a static content method and a
dynamic content method. In a static content method, the document is
created in advance and stored statically on a server database. When
a client requests the document, the server retrieves the document
and transmits it over the network to the client. FIG. 1 is an
example in which the server retrieves the static data 30 from
database 28 and serves the data to the client 24. It is further
noted that conventional servers, and particularly Web servers, may
be configured to push the content to the client without receiving a
request. The static content method has an advantage of minimizing
the user's perceived response time, meaning the time between
requesting the document and seeing it rendered on a computer
screen. It has a disadvantage that all users who request the
document receive exactly the same content. With static content, the
server cannot respond to specific user requests or personalize a
document for individual users.
In a dynamic content method, the document is generated dynamically
by the server. When a client requests a document, the server
invokes one or more agents, feeding the agents relevant parameters
from the user's request (such as the user's name). The agent(s)
generate the document that satisfies the user's request and the
server returns the document over the network to the client. The
dynamic content method has the advantage of
responding to specific user requests or personalizing content for
individual users. It has the disadvantage that the user's perceived
response time will generally be longer than with static document
requests. This is because the document generation process involves
additional time to invoke the appropriate agent(s) and generate the
document.
The server generates dynamic content documents by invoking an agent
in one of two ways: an "out-of-process" method and an "in-process"
method. In an "out-of-process" method, the agent runs in its own
process and address space, separate from the server's process and
address space. Typically, the out-of-process method uses the
industry-standard common gateway interface (CGI) as the
communication mechanism between the server and agent. CGI is
described in a publicly available document on the Web at
http://hoohoo.ncsa.uiuc.edu/cgi. In an "in-process" method, the
agent runs within the Web server's process and address space. The
in-process method typically uses a vendor-specific application
programming interface, like the Internet Server Application
Programming Interface (ISAPI) implemented by Internet Information
Server (IIS), which is available from Microsoft Corporation. The
ISAPI technology is described in more detail in a document at
http://www.microsoft.com/iis/Support/iishelp/iis/misc/documentation.asp.
To illustrate the two dynamic content methods and how they can be
used in conjunction with the static content method, consider a
scenario in which the server 22 runs a Web server for an online
retail company. When the client 24 first accesses the Web site, the
server 22 might retrieve a pre-existing home page for the company
from the database 28 and serve that page to the client 24. This
initial step is an example of a static content method. From the
home page, the client might request to view an online catalog of
products offered by the company. In response, the Web server might
invoke a catalog agent to guide the user through various product
offerings. When the user decides to purchase a product, the client
submits an order request. In response, the Web server might invoke
an order agent to assist the user in ordering the product. The
steps involved with actively serving a catalog or taking an order
are examples of dynamic content methods. They both involve dynamic
generation of documents in response to input received from the
client.
FIG. 2 shows an "out-of-process" method under this scenario. The
server 22 runs a Web server 40 as process 1. The Web server 40
handles the incoming requests from the client. When the client
first hits the Web site, the Web server 40 retrieves the company's
home page 42 from the database 28 and transmits the home page 42 to
the client. When the client sends an order request, the Web server
40 initiates an order manager 44 to assist the user with ordering
the desired product or service. The order manager 44 is initiated
using the CGI technology as a second process 2, which uses a
separate process and address space than process 1, as represented
by the dashed lines.
When the user selects an item, the order manager 44 dynamically
generates an order document 46 that contains the user's name, a
description of the selected item, the cost of the item, and payment
terms. The order manager 44 returns the order document 46 to the
Web server 40, which then serves the document 46 to the client.
Afterwards, the order manager 44 is terminated and the second
process 2 is halted.
The out-of-process method shown in FIG. 2 has an advantage in crash
prevention and recovery. If the out-of-process order manager 44 is
unreliable and ultimately crashes, it will not cause the Web server
40 to crash. However, the out-of-process method has a disadvantage
in that a particular agent must be loaded into memory each time a
request arrives for it. Using CGI technology, the agent must also
be unloaded from memory once it finishes the request. This loading
and unloading consumes resources, resulting in a relatively slow
response time. Another problem compounding the slowness is that the
out-of-process method involves cross-process communication between
processes 1 and 2, including such activities as marshalling,
messaging, and the like.
A variation of CGI, known as FastCGI, allows the server to keep the
agent loaded, rather than terminating the agent each time it
responds to a particular request. FastCGI is an improvement over
CGI in that it saves the per-request invocation overhead, thereby
improving the response time. However, the FastCGI is still run in a
separate process, and hence the drawbacks associated with
cross-process communication remain. A more detailed discussion of
FastCGI is found at
http://www.fastcgi.com/kit/doc/fastcgi-whitepaper/fastcgi.htm.
FIG. 3 shows an "in-process" method under the same scenario of the
online retail company. In this case, when the client sends an order
request, the Web server 40 initiates an order manager 48 to assist
the user with ordering the desired product or service. The order
manager 48 is initiated using the ISAPI technology to run within
the same process 1 as the Web server 40. That is, the Web server 40
and the order manager 48 use the same process and address space
designated by the server. When the user selects an item from the
online catalog, the order manager 48 dynamically generates an order
document 50 that contains the user's name, a description of the
selected item, the cost of the item, and payment terms. The order
manager 48 returns the order document 50 to the Web server 40,
which then serves the document 46 to the client. The order manager
48 can remain loaded for other requests, or terminated when
desired.
The in-process method is advantageous in that a particular agent
need only be loaded into memory once, when the first request
arrives for it. The agent can then remain in memory within the
server's process and address space, and can handle additional
requests that arrive for it. The in-process method has a further
advantage in that there is no need for cross-process communication.
As a result, the in-process method is comparatively faster than the
out-of-process method. However, the in-process method has the
disadvantage that if the agent is unstable and crashes, it will
cause the server to crash too.
Most large Web sites and many smaller ones deliver one or more
applications in the traditional information system sense. A site
that supports catalog shopping, library browsing or database access
will typically consist of many separate agents and documents that
together implement the site's "capplication"; in other words, the
unified experience presented by the Web site to the user. The
developer of such a site needs a mechanism to organize an
application's software components to enforce consistency,
compatibility, version control, and other requirements across
components. It is also desirable to construct high performing
agents because they often provide the most appealing content
delivered by the Web site. The agents are often required to process
more than their proportionate share of user requests. Agents that
perform slowly may cause users to abandon a Web site because they
become frustrated with slow response times, no matter how appealing
the content might be.
A Web site developer is also interested in protecting the site
against system or process crashes. A Web server can host many Web
applications. The applications may be hastily developed and, while
effective at certain tasks, may perform unpredictably when
subjected to high volume or wide variety of user requests at an
active Web site. If not guarded against, such unpredictable
applications may bring down the entire site. Accordingly, a
developer would like to be able to isolate "trusted" components
(i.e. components that are fully tested, debugged, and judged to be
crash proof in normal operation) from non-trusted components.
Another advantage of isolated application is that you can stop and
unload application components from memory without interfering with
the operation of the Web site. Stopping an isolated application is
an extremely convenient way to install new components because you
don't have to stop and restart the web server to stop and restart
an application.
Accordingly, there is a need in the industry to further improve the
dynamic content methods for serving documents and other data to
clients. There is a need to develop an architecture which enables
Web site developers to create high performing agents, to organize
the agents in functional groups for optimal performance at a given
Web site, and to design isolation between the trusted agents and
the non-trusted agents.
SUMMARY OF THE INVENTION
This invention concerns a server architecture that improves dynamic
content methods for generating client responses. The architecture
groups processing agents into functional collections according to
their underlying functionality. Thus, agents can be grouped
according to the applications supported by the server. As an
example, a designer of a Web site is able to group agents that
process requests to navigate a catalog into one collection, and
agents that process requests for ordering into another collection,
and agents that process requests for customer service into a third
collection.
The server architecture provides a managerial hierarchy to manage
the agents and to control how the client requests are handled. An
application manager manages each collection of agents. The agents
within the associated collection are independent from, but
dynamically accessible by, the application manager. Depending on
the request, the application manager selects one or more agents to
generate content to be returned to the client. In this manner, the
application manager and associated agents under its control form an
application, such as a catalog application, an ordering
application, a customer service application, and so forth.
An application manager director manages the application managers.
The application managers are independent from, but dynamically
accessible by, the application manager director. Depending on the
request, the director selects the appropriate application manager
to handle the request, which in turn selects the appropriate agent
to process the request. According to the managerial hierarchy, the
director first decides which server application is best suited to
handle the incoming request, and then the application manager
within the chosen server application decides which specific agent
should process the request.
The director can be implemented as part of the general server
software. The separate server applications (i.e., the agents and
associated application managers) can be run either in-process or
out-of-process with the server software. An in-process application
offers higher performance at the risk of crashing the system if one
agent performs unreliably. An out-of-process application affords
high reliability and crash protection at the expense of lower
performance due to cross-process communication.
The server architecture allows a designer to separate trusted
agents from non-trusted agents. Trusted agents and their
application manager can be run in-process with the server software
to improve performance. Meanwhile, non-trusted agents and their
application manager can be run out-of-process from the server
software until they prove themselves reliable. If the non-trusted
agents ultimately prove to be trusted, they can be moved in-process
with little adaptation.
BRIEF DESCRIPTION OF THE DRAWINGS
The same reference numbers are used throughout the figures to
reference like components and features.
FIG. 1 is a diagrammatic illustration of a client-server
system.
FIG. 2 shows a Web server software program executing on a server
computer, and an out-of-process agent invoked by the Web server to
dynamically generate a document in response to a client request,
according to conventional techniques.
FIG. 3 shows a Web server software program executing on a server
computer, and an in-process agent invoked by the Web server to
dynamically generate a document in response to a client request,
according to conventional techniques.
FIG. 4 shows a server software architecture according to an aspect
of this invention.
FIG. 5 shows a block diagram of a server computer used to implement
the server software architecture.
FIGS. 6-8 show steps in a method for handling client requests
according to another aspect of this invention.
DETAILED DESCRIPTION
FIG. 4 shows a server software architecture 60, which executes on a
server computer, to facilitate client-server sessions between the
server computer and a remote client computer (not shown). The
architecture 60 is particularly well suited for accommodating
dynamic content sessions in which the server dynamically generates
and serves a response that is tailored to client. The architecture
60 may be implemented in a number of server environments. For
purposes of discussion, the architecture 60 is often described in
the exemplary context of an Internet setting, wherein the server
program is configured as a Web server at a Web site on the
Internet. However, aspects of this invention are not restricted to
the Internet environment, but may include other contexts including
client-server LANs (local area networks), interactive television,
and so forth.
The server architecture 60 includes a server software program 62
that executes on a computer to receive requests from clients and
return responses to those clients. An example of a server software
program 62 is the Microsoft Internet Information Server (IIS),
which runs on a server operating system such as Microsoft Windows
NT. Microsoft IIS and Microsoft Windows NT are well known software
products from Microsoft Corporation.
The architecture 60 also includes one or more application managers
(AMs), as represented by application managers 64(1), 64(2), and
64(3). Each application manager 64 instantiates an "application"
developed to run in conjunction with the server 62. Each
application manager 64 manages one or more agents 66 that implement
the functionality underlying the application manager 64.
Conceptually, the application manager 64 is a dynamic processor of
client requests that uses one or more agents to generate content to
be returned to the client. The application manager 64 dynamically
loads associated agents 66 as needed to handle particular user
requests. The application manager 64 can handle an arbitrary number
of user requests at a time, and it can load and maintain an
arbitrary number of agents 66 into its address space in order to
process user requests.
Consider a Web related example, in which the server 62 is
configured as a Web server. One application manager 64(1) might be
a catalog shopping application containing a first agent 66(1,1)
that queries an inventory database to compose catalog pages, a
second agent 66(1,2) that presents the user with an order form, and
so forth. A second application manager 64(2) might be customer
service application containing a first agent 66(2,1) that composes
a series of help pages, a second agent 66(2,2) that handles
requests to return merchandise, and so on. A third application
manager 64(3) might offer another service supported by the Web
server 62.
The application managers 64 may run within the server's process
(i.e., in-process), or within its own separate process (i.e.,
out-of-process) either on the same machine as the server or on a
different machine. In FIG. 4, application managers 64(1) and 64(2)
are in-process with the server program 62, whereas application
manager 64(3) is out-of-process with the server program 62.
In-process applications allow maximum efficiency at the risk of
bringing down the server in the event that the application is not
stable. Alternatively, out-of-process applications are effectively
isolated so that if an application fails, it should not affect the
running of the server. However, this isolation benefit comes at the
cost of lower performance when compared to an in-process
application. The server architecture 60 advantageously offers the
developers the flexibility to run either or both in-process and
out-of-process applications.
In one exemplary implementation, each application manager 64 is
embodied as an object using ISAPI technology, and hence can remain
loaded, regardless of whether it is in-process or out-of-process
with the server 62. Each AM object 64 communicates with an
associated agent 66 via an ISAPI interface 68. It is noted,
however, that this invention may be implemented using technology
other than ISAPI.
The server architecture 60 has an application manager director 70
to manage the application managers 64(1)-64(3) and their agents 66.
The AM director
70 determines which application manager 64(1)-64(3) should service
a given client request. The AM director 70 also starts and stops
the application managers as required by user requests. The AM
director 70 can stop, pass, and unload the application managers and
agents that are running. Another task of the AM director 70 is to
detect when the out-of-process application manager 64(3) has
crashed and optionally, to attempt to re-start the failed
manager.
The AM director 70 maintains a lookup table 72 listing all active
application managers. Entries in this table 72 reference an object
for each corresponding active application manager 64(1)-64(3).
Table 72 contains an object AMInfo 74(1) and 74(2) for each of the
in-process application managers 64(1) and 64(2), and an object
AMInfoOOP for the out-of-process application manager 64(3). These
objects 74 contain data and parameters to communicate with the
associated application managers.
When a client request arrives, the application manager director 70
determines which application manager 64 ought to handle the
request. Once an application manger is selected, the AMInfo object
associated with the selected application manager creates a new
request object 80 containing the data in the client request that
will be processed by an agent 66. More particularly, the request
object 80 holds request-specific information, such as user name,
network connection, callback information, and so forth. The AMInfo
object then passes the request object 80 to the AM object 64 for
execution.
Numerous request objects can exist simultaneously, as represented
by request objects 80(1,1), 80(1,2), and 80(1,3) directed to
application manager 64(1), request objects 80(2,1) and 80(2,2)
directed to application manager 64(2), and request objects 80(3,1)
and 80(3,2) directed to application manager 64(3). In one
imaplementation, the AM object 64 invokes a single agent 66 for
each corresponding request object 80. However, this condition need
not be met in other implementations.
The request objects 80 communicate with the AM objects 64 via a
marshalable interface 82. This means that, optionally, the
parameters of a method call to the interface 82 of either the AM
object 64 or the request object 80 can be copied and passed by
value, instead of being passed by reference. Hence, the interface
82 can optionally be used in-process or out-of-process. Marshalling
lets the AM director 70 decide at runtime whether to route a
request to an in-process or an out-of-process AM object.
Various types of technologies support the marshalable interface 82.
As one example, the AM and request objects can be based on COM
(component object model) and RPC (remote procedure call)
technologies. These technologies provide generic mechanisms for
allowing objects to communicate with each other solely through
interfaces, with no knowledge of the other object's internal data
structure, and optionally across process boundaries.
At the object level, there is little difference whether the AM
objects 64 are in-process or out-of-process. The same data is
communicated between the request objects 80 and the AM objects 64,
regardless of whether there is a process boundary between them. The
difference between in-process and out-of-process methods is
manifest at the marshalable level. To communicate across a process
boundary, as is the case between request objects 80(3,1), 80(3,2)
and the AM object 64(3), the marshalable interface 82 might employ
either a stub and proxy protocol or RPC. COM, stub and proxy, and
RPC are all well known. In addition, the objects might employ other
technologies that permit process isolation, such as the DCOM
(distributed component object model) technology.
When a request object 80 is handed off to an application manager
64, the application manager 64 creates a corresponding shadow
object (SO) 84. The shadow object 84 contains a subset of the data
in the corresponding request object 80, along with information on
how to report back to the request object. For each active shadow
object 84, the application manager 64 invokes a suitable agent 66
to process the request data in the shadow object. If more data from
the request is needed, the shadow object 84 returns to the request
object 80 to obtain the additional data. From the agent's
perspective, it is unaware whether the data is from the shadow
object 84, or whether the shadow object had to callback to the
request object 80 and obtain the data. The agent 66 passes the
results back to the application manager 64, which in turn passes
the results to the request object 80.
The application manager director 70, the application managers 64,
and the agents 66 form a dynamic content generation system that
handles client requests which involve dynamic generation of
content. That is, the server 62 will determine what type of
response is needed for the request. If a static content response is
in order (e.g., serving a home page), the server 62 can bypass this
System and simply serve a pre-existing static response to the
client. Conversely, if the client request requires something more
than pre-existing static data, the server uses the dynamic content
generation system to create the appropriate response using the
information in the client request.
Tables 1-3 list primary data structure elements for the various
objects in the server architecture 60. A data structure for the AM
object 64 is shown in table 1.
TABLE 1 ______________________________________ Application Manager
Object ______________________________________ Reference count Flag
indicating whether application manager is in- process or
out-of-process Table of running agents List of shadow objects for
requests currently being processed
______________________________________
A data structure for a request object 80 is shown in table 2.
TABLE 2 ______________________________________ Request Object
______________________________________ Reference count Pointer to
server's native request object Pointer to application manager which
will process the request. Cover functions for server methods.
Pointer to shadow object for pending asynchronous input/output
operation, if any. ______________________________________
A data structure for a shadow object 84 is shown in table 3.
TABLE 3 ______________________________________ Shadow Object
______________________________________ Reference count Pointer to
request object State information for pending asynchronous
input/output operation, if any.
______________________________________
FIG. 5 shows an example implementation of a server computer 100,
which can be used to implement the server architecture 60. The
server 100 includes a processing unit 102, a system memory 104, and
a system bus 106 that interconnects various system components,
including the system memory 104 to the processing unit 102. The
system bus 106 may be implemented as any one of several bus
structures and using any of a variety of bus architectures,
including a memory bus or memory controller, a peripheral bus, and
a local bus.
The system memory 104 includes read only memory (ROM) 108 and
random access memory (RAM) 110. A basic input/output system 112
(BIOS) is stored in ROM 108.
The server 100 has one or more of the following drives: a hard disk
drive 114 for reading from and writing to a hard disk or hard disk
array; a magnetic disk drive 116 for reading from or writing to a
removable magnetic disk 118; and an optical disk drive 120 for
reading from or writing to a removable optical disk 122 such as a
CD ROM or other optical media. The hard disk drive 114, magnetic
disk drive 116, and optical disk drive 120 are connected to the
system bus 106 by a hard disk drive interface 124, a magnetic disk
drive interface 126, and an optical drive interface 128,
respectively. The drives and their associated computer-readable
media provide nonvolatile storage of computer readable
instructions, data structures, program modules and other data for
the server 100.
Although a hard disk, a removable magnetic disk 118, and a
removable optical disk 122 are described, other types of computer
readable media can be used to store data. Other such media include
magnetic cassettes, flash memory cards, digital video disks,
Bernoulli cartridges, random access memories (RAMs), read only
memories (ROM), and the like.
A number of program modules may be stored on the hard disk,
magnetic disk 118, optical disk 122, ROM 108, or RAM 110. These
programs include a server operating system 130, one or more
application programs 132, other program modules 134, and program
data 136. The operating system 130 is preferably the Windows NT
server operating system, although other types of operating systems
may be used, such as a UNIX-based operating system. The server
architecture 60 shown in FIG. 4 can be incorporated into the
operation system 130, or implemented as separate applications 132
or program modules 134.
An operator may enter commands and information into the server 100
through input devices, such as a keyboard 138 and a mouse 140.
Other input devices (not shown) may include a microphone, joystick,
game pad, satellite dish, scanner, or the like. These and other
input devices are connected to the processing unit 102 through a
serial port interface 142 that is coupled to the system bus 106,
but may alternatively be connected by other interfaces, such as a
parallel port, game port, or a universal serial bus (USB).
A monitor 144 or other type of display device is also connected to
the system bus 106 via an interface, such as a video adapter 146.
The server computer 100 has a network interface or adapter 148, a
modem 150, or other means for establishing communications over a
network 152.
It is noted that the computer shown in FIG. 5 is just one possible
type of computing device that can be used to implement this
invention. Other computing devices may also be used to implement
the invention.
FIGS. 6-8 show steps in method for handling requests from a remote
client. The steps are described in the context of the server
architecture illustrated in FIG. 4. These steps are performed by
the various software components during execution on the server
computer of FIG. 5.
At step 200, the server 62 receives a request from a client. The
server 62 analyzes the client request to determine how to satisfy
the request (step 202). If the server 62 can satisfy the client
request with a static content response, such as serving a
pre-existing document, the server 62 will retrieve the static data
and serve that data to the client (step 204).
If the server 62 determines that the client request requires a
dynamic content response and thus involves invoking an application,
the server 62 forwards the request to the application manager
director 70 (step 206). The director 70 creates a request object 80
to hold the request data (step 208). The director 70 then
determines which application manager 64 should process the request
and whether the application manager 64 should be run in-process or
out-of-process (step 210).
Once the specific application manager is selected, the application
manager director 70 determines whether that application manager is
already running (step 212). If not (i.e., the "no" branch from step
212), the director 70 starts the required application manager 64
and adds it to the director's table 72 of active application
managers (step 214).
If the application manager is in-process (e.g., AM object 64(1)),
the director 70 calls a process function in the AM object 64(1) and
passes in an interface pointer to the request object (e.g., request
object 80(1,1)) (step 216).
On the other hand, if the application manager is out-of-process
(e.g., AM object 64(3)), the director 70 calls an in-process proxy
for the out-of-process AM object 64(3) (step 220). The director 70
passes to the proxy the interface pointer to the request object
(e.g., request object 80(3,1)) (step 222). The proxy then marshals
parameters and makes the cross-process call via COM and RPC to the
out-of-process stub for the AM object 64(3) (step 224). COM creates
a proxy for the request object 80(3,1) within the out-of-process
space (step 226). The AM object's stub un-marshals the parameters
and calls the process function in the AM object 64(3), passing in
the request object's proxy as one of the parameters (step 228).
The selected application manager (e.g., in-process AM object 64(1)
or out-of-process AM object 64(3)) creates a shadow object 84 for
the corresponding request (step 230). The application manager 64
increments the reference count of the request object 80 (or proxy,
if the AM object is running out-of-process) (step 232), and stores
the request object's (or proxy's) interface pointer in the shadow
object (step 234).
The application manager 64 determines which agent 66 should be
invoked to satisfy the particular request (step 236). The
application manager 64 then determines whether the desired agent is
already running (step 238). If not, the application manager loads
the agent and adds it to the AM object's table of running agents
(step 240).
The application manager invokes the selected agent 66, passing it
information about the user's request (step 242). The agent 66 then
processes the request using the data in the newly created shadow
object 84 (step 244).
In the described implementation, the application manager receives
any calls made by the agent 66 for server services via the ISAPI
callback functions. For example, the agent 66 could call back to
read information from or write information to the request's network
connection, or get information like user name or browser type for
the request. If the application manager is running in-process, the
application manager uses the interface pointer to the request
object to invoke a method that is appropriate to handle the agent's
callback. If the application manager is running out-of-process, the
application manager uses the interface pointer to the proxy for the
request object to invoke a method appropriate to the agent's
callback.
When the agent 66 indicates that it has finished processing the
request (e.g., by calling a particular interface to the application
manager), the agent passes the results back out to the application
manager, which in turn passes the results back to the server 62
(step 248). The application manager 64 destroys the shadow object
84 (step 250) and decrements the reference count of the request
object (or proxy) (step 252). When the request object's reference
count reaches zero, it destroys itself (step 254).
The server architecture 60 is beneficial in that it allows the
flexibility to run an agent or a collection of agents in-process
for highest performance, or out-of-process for highest reliability.
Even when run out-of-process, the agents and application managers
can remain loaded between user requests, thereby improving
performance as compared to the conventional load-and-unload of
CGI.
One advantage afforded by the server architecture 60 is that a
designer can separate trusted agents from non-trusted agents.
Trusted agents and their application manager can be run in-process
with the server software to improve performance. Meanwhile,
non-trusted agents and their application manager can be run
out-of-process from the server software until they prove themselves
reliable. If the non-trusted agents ultimately prove to be trusted,
they can be moved in-process with little or no adaptation.
In addition, the architecture 60 enables developers to organize
the
applications, as desired, to enforce consistency, compatibility,
version control, and other requirements across components.
Although the invention has been described in language specific to
structural features and/or methodological steps, it is to be
understood that the invention defined in the appended claims is not
necessarily limited to the specific features or steps described.
Rather, the specific features and steps are disclosed as exemplary
forms of implementing the claimed invention.
* * * * *
References